The present invention relates to a method according to the preamble of claim 1 and an apparatus according to the preamble of claim 5 for producing a seal including a tubular section of an elastomeric material with a wall of variable thickness.
U.S. Pat. No. 5,162,090A discloses a method and an apparatus of this type wherein an obturator is displaceable on the terminal die plate, between a passive position in which it does not interfere with the tubular extrudate exiting from the die and closes an escape passage in the die, and an active position in which it engages and deforms the extrudate on one side causing a modification of the cross-section thereof from an O-shape to a D-shape. In the active position the obturator opens the escape passage of the die and the elastomeric material which flows therethrough allows to compensate the increase of the back pressure in the extruder which is due to the overall reduction of the cross-sectional area of the tubular extrudate.
One object of the present invention is to provide improved method and apparatus of the initially defined kind.